Abstract
The effect of postharvest chitosan, gallic acid (GA) and chitosan gallate (CG) dipping treatments at different concentrations on quality parameters, antioxidant compounds, free radical scavenging capacity (FRSC) and enzymes activities of 'Sukkari' bananas were studied during storage (ripening) at 20 ± 2 °C and 60-70% RH for 13 days. Weight loss and peel color index (the change from green to yellow) increased while, membrane stability index of peel tissues, pulp firmness and acidity decreased during storage. CG and GA treatments slowed down the changes in these parameters compared to control. Total soluble solids (TSS) concentration increased during storage and was lower at CG than other treatments. TSS/acid ratio increased during storage and showed higher value after storage than initial. This ratio was lower at 1% chitosan, 0.075% GA and CG treatments than control. Both vitamin C and total flavonoids concentrations decreased during storage and were not affected by the applied treatments. Total phenols concentration decreased during storage and was higher at acetic acid and the high rate of chitosan, GA and CG treatments than control. FRSC (DPPH IC50 values) of fruit peel ranged from 2.54 to 4.19 µg phenolics concentration among the treatments. FRSC was not affected by the applied treatments but increased (lower IC50 value) during shelf life. The possible relations of these biochemical changes with the activities of the enzymes α-amylase, xylanase, polygalacturonase, peroxidase and polyphenoloxidase were discussed. It is concluded that postharvest CG and GA treatments delayed ripening and maintained better quality parameters of 'Sukkari' bananas during 13 days of shelf life than control.